The overall goal of the proposed research is to examine the nature of the relationship between two disorders, reading disability (RD) and phonological disorder (PD). Although there is evidence that these disorders overlap at symptomatic, cognitive, and etiological levels, the reason for this overlap is currently unclear. The proposed study will examine overlap at these levels of analysis in a sample of RD and control children, some of whom had earlier PD, in order to further elucidate the nature of the cognitive and etiological relation between these disorders. Four competing hypotheses will be tested through the comparison of group performance on a number of cognitive tasks, and through behavioral genetics analyses. These hypotheses, the severity, pleiotropy, cognitive phenocopy, and RD subtype hypotheses, each posit different combinations of etiological and cognitive influences to account for the shared overlap between RD and PD. Further, several subtypes have been identified for both RD and PD. The relations between these subtypes will be explored in order to determine which of the subtypes of each of these disorders are most related to each other. Psychiatric correlates of each of these disorders, and of the overlap between RD and PD, will also be examined in order to further characterize children who meet diagnostic criteria for these disorders.